An optoelectronic component assembly is described, for example, in U.S. Pat. No. 5,283,434. The component assembly is used in the compact scanning unit of an optical position-measuring device, with the aid of which a measuring graduation is scanned and scanning signals, modulated as a function of displacement, are generated. The component assembly illustrated in FIG. 1c includes a carrier structure, called carrier element in the following, made of ceramic and having a recess, an optoelectronic component in the form of a light source configured as an LED being positioned in the central bottom region of the recess. Adjacent thereto, further optoelectronic components taking the form of photoelements are placed in the region of the recess. A transparent cover element formed as a glass plate is arranged over the recess. In several partial areas, the cover element has structurings in the form of periodic diffraction-grating structures. They act as a transmitting graduation in front of the LED and as scanning graduations in front of the photoelements.
An optoelectronic component assembly arranged in this manner may have a number of disadvantages. The complete ceramic carrier element having the various elements must be arranged i.e., adjusted on another carrier for further placement in the scanning unit of an optical position-measuring device. Significant expenditure with respect to precise adjustment of the complete component assembly in several method steps therefore results during manufacture and assembly. Moreover, a number of complicated adjustment processes are also necessary within the component assembly. In particular, the precise relative positioning of the cover element and the structurings arranged thereon in relation to the various optoelectronic components requires a high expenditure on the assembly side. Another disadvantage of this component assembly is that, altogether, a relatively high system results, which may lead to damage if the scanning distances between the scanning unit and the scale are small.
A further optoelectronic component assembly from the scanning unit of an optical position-measuring device is described in Japanese Published Patent Application No. 9-189514. The component is arranged on a carrier element and is surrounded by a circumferential frame or dam. A partial area of the component surface is covered by a glass plate resting thereon. The inner space of the dam is also filled with a sealing compound. A disadvantage in this is that, particularly in the boundary region between the glass plate and the sealing compound, an unwanted ion diffusion may take place in the direction of the component and influence it disadvantageously. Moreover, in response to temperature fluctuations, the adhesion bond in the boundary region does not satisfy the mechanical demands because of different expansion coefficients.
Another optoelectronic component assembly is described in European Published Patent Application No. 0 184 628. Reference is made in particular to FIG. 3. Problems with respect to the correct adjustment of the cover element in relation to the further components results in this assembly, as well.
In addition, reference is made, for example, to FIG. 1B of German Published Patent Application No. 198 43 155.
In summary, the approaches mentioned for optoelectronic component assemblies may not be optimal with respect to the necessary adjustment of the cover element and possibly with respect to the adjustment of the complete component assembly, as well as with respect to its protection from environmental influences during actual operation.